1. Field of the Invention
The present invention relates, in general, to perfluorostyrene compounds, and coating solutions and optical waveguide devices using the same. In particular, the present invention is directed to a fluorine compound having perfluorostyrene moiety, and a coating solution and an optical waveguide device using the same. These fluorinated compounds are applied for a core and a cladding material of various planar optical waveguide devices, such as optical switches, variable optical attenuators (VOA), tunable and fixed wavelength filters, arrayed waveguide grating (AWG) devices, etc.
2. Description of the Related Art
Generally, polymeric optical waveguide devices should be required the reliability based on Telcodia test for the optical communication network. In such a case, the polymer material should have very high thermal stability and environmental stability. Further, there are required accurate control of a refractive index and low birefringence as well as low optical propagation loss at a telecommunication wavelength region. Furthermore, in order to fabricate a desirable optical device, the polymer material should have excellent adhesion to any substrate. Of the above-mentioned requirements, the optical propagation loss and the birefringence are regarded as very important characteristics. The optical propagation loss on a polymer thin film is mainly caused by the light absorption by a harmonic overtone vibration mode of a C—H bond in the presence of polymer. Such light absorption at wavelengths of near far infrared can be decreased by substituting deuterium (D) or halogen elements, such as fluorine (F), for hydrogen of C—H bond (or O—H, N—H), whereby an absorption wavelength band can be shifted to 5–25 μm. Therefore, the loss can be lowered at communication wavelengths.
On the other hand, the birefringence of the thin film is caused by a molecular structure and a stress of a thin film-preparing process.
Accordingly, various polymer materials have been developed to meet all the requirements. In this regard, a fluorinated polyimide compound, which is known to have excellent heat resistance, even at about 400° C., has been continuously applied for optical waveguide devices (U.S. Pat. No. 5,598,501, Macromolecules, vol 27, pp 6665, 1994 and Electronics Letters, 29(3) 269, 1993). However, polyimide suffers from drawbacks, such as relatively high optical loss of 0.7 dB/cm or more and a high birefringence of 0.008 or more.
As another polymer material, there is proposed UV-curable fluorinated acrylate including various compositions, which is advantageous in terms of relatively low optical loss of 0.3 dB/cm at 1.55 μm and a birefringence of 0.0008. (U.S. Pat. No. 6,306,563 B1, and IEEE Journal of selected topics in quantum electronics vol. 6, pp 54, 2000).
As still another polymer material, there is proposed fluorinated polyarylene ether having a low dielectric constant, and excellent mechanical strength and processability (U.S. Pat. No. 5,115,082), which shows the possibility as a potential optical polymer. In addition, the above polymer system is added with a thermally curable reactive group, to drastically increase chemical resistance, whereby such a polymer is applied for the optical waveguide device (Korean Patent No. 226,442). Consequently, fluorinated polyarylene ether based polymers have been further improved in optical loss (0.4 dB/cm) and birefringence (0.004), compared to polyamide-based polymers, but is disadvantageous of still high birefringence and high processing temperatures (280° C. or more).